The plan is to test the hypothesis that sufficient porosity can be created in thin tissue sections to move reactants dynamic perfusion. This is expected to require control of the freezing rate in lyophilization and use of proprietary microporous film technology. At present reagents are introduced in tissue sections by static diffusion. The proposed vertical flow of fluid through "microchannelled" tissue by means of pulsed filtration is expected to improve the efficiency of cell analyses. This should reduce assay costs, improve accuracy, and streamline automation. In phase I, the focus will be to maximize assay efficiency,based on perfusion, for immunocytochemistry and in situ hybridization. The idea is to develop the necessary devices to facilitate the transition to a perfusional assay format. This would serve both the manual system that uses microscope slides and a proposed automated system that uses "Tissue Discs".